Photonic crystal waveguide arrays

A waveguide device for an optical signal comprising;

• a slab of dielectric medium;
• a latticed region formed in the dielectric medium by a periodic array of lattice sites comprising localised structures having dielectric properties which are different from those of the surrounding medium, the periodic array being dimensioned such that a photonic bandgap exists in the latticed region inhibiting propagation of the optical signal therethrough;
• and
• a waveguide region formed in the dielectric medium by discontinuities in the periodic array of lattice sites allowing propagation of the signal therethrough;
• wherein the waveguide region defines an input region for the input of the optical signal, an output region for the output of the optical signal and a plurality of optical pathways for conducting respective components of the optical signal between the input and output regions;
• and
• comprising modulating means operable to variably control transmission through a plurality of the optical pathways to adaptively define a transfer function of equalization applied to frequency components of the optical signal.

A waveguide device for an optical signal comprising;

• a slab of dielectric medium;
• a latticed region formed in the dielectric medium by a periodic array of lattice sites comprising localised structures having dielectric properties which are different from those of the surrounding medium, the periodic array being dimensioned such that a photonic bandgap exists in the latticed region inhibiting propagation of the optical signal therethrough;
• and
• a waveguide region formed in the dielectric medium by discontinuities in the periodic array of lattice sites allowing propagation of the signal therethrough;
• wherein the waveguide region defines an input region for the input of the optical signal, an output region for the output of the optical signal and a plurality of optical pathways for conducting respective components of the optical signal between the input and output regions;
• wherein the waveguide region defines a cavity bounded by a boundary surface at the transition between the latticed region and the waveguide region and a plurality of waveguides communicating with the cavity at different locations on the boundary surface, the cavity being formed with a linearly extending portion of the boundary surface;
• and
• wherein the waveguide region further defines an input waveguide communicating with the cavity and positioned to direct the optical signal into grazing incidence with the linearly extending portion for creating surface wave propagation of the optical signal propagating in proximity with the linearly extending portion.

A method of applying equalization to an optical signal comprising the steps of;

• inputting the optical signal to an input region of a waveguide device;
• conducting components of the optical signal to an output region of the waveguide device via a plurality of respective optical pathways defined by the waveguide device;
• and
• outputting the optical signal from the output region;
• wherein the step of conducting the components of the optical signal comprises inhibiting propagation of the optical signal through a latticed region formed by a periodic array of lattice sties defining a photonic bandgap and propagating the components of the optical signal via a waveguide region formed by discontinuities in the periodic array of lattice sites;
• wherein the waveguide region defines a cavity bounded by a boundary surface at the transition between the latticed region and the waveguide region, the cavity communicating with the input region and the output region;
• and
• wherein the boundary surface constitutes a plurality of reflectors directing respective components of the optical signal via respective pathways between the input region and the output region.

A method of applying equalization to an optical signal comprising the steps of;

• inputting the optical signal to an input region of a waveguide device;
• conducting components of the optical signal to an output region of the waveguide device via a plurality of respective optical pathways defined by the waveguide device;
• modulating transmission through at least one of the optical pathways to thereby modulate a respective component of the optical signal;
• and
• outputting the optical signal from the output region;
• wherein the step of conducting the components of the optical signal comprises inhibiting propagation of the optical signal through a latticed region formed by a periodic array of lattice sties defining a photonic bandgap and propagating the components of the optical signal via a waveguide region formed by discontinuities in the periodic array of lattice sites;
• and
• wherein the modulating step comprises variably controlling transmission through a plurality of the optical pathways to adaptively define a transfer function of equalization applied to frequency components of the optical signal.

A method of dividing an optical signal into a plurality of components for conduction via respective waveguides comprising the steps of:

• inputting the optical signal into a waveguide region defined by discontinuities in a latticed region in which propagation is inhibited by a photonic band gap;
• directing the optical signal into grazing incidence with a linearly extending surface defined by a transition between the latticed region and the waveguide region so that surface wave propagation of the optical signal occurs in proximity with the linearly extending surface;
• deflecting portions of the surface wave by scattering from the linearly extending surface;
• and
• conducting the deflected portions into said waveguides.

An optical communications system comprising at least one waveguide device for an optical signal, said at least one waveguide device comprising:

• a slab of dielectric medium;
• a latticed region formed in the dielectric medium by a periodic array of lattice sites comprising localised structures having dielectric properties which are different from those of the surrounding medium, the periodic array being dimensioned such that a photonic bandgap exists in the latticed region inhibiting propagation of the optical signal therethrough;
• a waveguide region formed in the dielectric medium by discontinuities in the periodic array of lattice sites allowing propagation of the signal therethrough;
• and
• a line amplifier operable to amplify said optical signal;
• wherein the waveguide region defines an input region for the input of the optical signal, and output region for the output of the optical signal and a plurality of optical pathways for conducting respective components of the optical signal between the input and output regions;
• and
• wherein said waveguide device constitutes a component of said line amplifier.